The present invention relates to a vane axial air mover which comprises a motor that drives an impeller to generate a flow of air through a flow path. More particularly, the invention relates to such an air mover which uses the pressure difference between the upstream and downstream ends of the flow path to cause a portion of the air to flow back through the motor in order to cool the motor.
Air movers typically include an electric motor which spins an impeller to generate a flow of air through a defined flow path. In certain types of air movers, such as axial fans, the motor is positioned in the flow path. However, since the size of the motor is largely driven by thermal concerns and its life is limited by the temperature capability of available insulation materials, fitting a motor with sufficient shaft power inside an optimal flow path is often a challenge. Consequently, the ability to dissipate heat from the motor is a design-limiting factor.
In some prior art fans, the motors are often cooled by air which is supplied by either an external blower or an internal fan. However, for low to medium power fans, the use of an external blower is not practical. Also, while internal fans can be somewhat effective in cooling the motor, they take up space and require a volume of air to draw from. Furthermore, although motors which are integrated into the axial fan assembly do dissipate some of their heat to the flow of air in the flow path due to “air over” cooling, the thermal resistance this heat dissipation path presents to the internal heat-generating motor components, such as coils, bearings, power electronics and rotor conductors, is very large.